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MODD / Mr. Hansen |
Name:
_________________________ |
Test on Unit 0x30 (Topics 0x29 and 0x31-0x3E, omitting
0x3F)
Time limit: 32 minutes (48 minutes for extended
time). A calculator is permitted.
Each question is worth 5 points. Your name is worth 3 points.
Instructions for Part I: For multiple choice questions, write the capital
letter of the best choice in the
blank provided. For fill-in problems, write the word or phrase that best fits
in the space provided.
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___ 1. |
PCM (pulse code modulation)
is a very general term that refers to all instances of . . . |
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(A) sampling followed by
quantization |
(D) choices (B) and (C)
combined |
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___ 2. |
Several types of phase
shift keying that could be used for wireless transmission of digital data are
. . . |
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(A) AM, FM, and HDTV |
(D) BPSK, QPSK, and DQPSK |
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___ 3. |
In PSK, the ________ of the
carrier wave indicates a binary 1 or 0. However, in DPSK, it is the
_______________ of the phase that indicates a binary 1 or 0. |
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(A) phase; change or
difference |
(D) amplitude; change or
difference |
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___ 4. |
Noise for
our purposes is defined as . . . |
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(A) loud sound |
(D) whispering |
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___ 5. |
ASK, FSK, and PSK are the
three basic techniques intended for . . . |
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(A) phase shift keying |
(D) compression of digital
data |
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___ 6. |
A 1-byte ASCII
representation can be any of how many possibilities? |
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(A) 21, or 2 |
(D) 216, or
65,536 |
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___ 7. |
CD-quality digital audio
requires a sampling rate of 44.1 KHz. This value was chosen because . . . |
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(A) human hearing extends
to about 40 KHz |
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___ 8. |
CD-quality stereo digital
audio, at a bit depth of 16 bits per sample and 44,100 samples per second,
has an uncompressed data requirement of approximately . . . |
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(A) 44 KB/sec |
(D) 172 KB/sec |
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___ 9. |
Nyquist’s Theorem states that the ________________ must be at
least double the highest analog frequency present in the original audio
source in order to avoid ____________ errors. |
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(A) bit rate; intermodulation distortion |
(D) sampling rate; aliasing |
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___10. |
An audio signal is at 35 watts,
and the noise level is 63 dB down. Find the noise level. |
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(A) 17.5 microwatts |
(D) 35 milliwatts |
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___11. |
Ohm’s Law can be used on .
. . |
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(A) resistive (R) circuits
only |
(D) all of the above |
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___12. |
A battery attempting to
supply 12 volts to a 35 KW resistive load will supply up to . . . |
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(A) 0.29 milliamps |
(D) 0.343 amps |
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___13. |
An AC adapter that provides
an output of 9 volts DC at 200 milliamps draws how much power? |
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(A) 1800 milliwatts (1.8 watts) |
(D) a little more than (A)
because of waste |
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Instructions for Part II: Write a free response for each question. The answers
can be quite short.
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14. |
Explain briefly why old
Western movies (shot at 24 frames per second) sometimes show wagon wheels
that appear to be stationary even though the wagon is moving. Please use a
diagram. |
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15. |
Convert the following hex
number to a little-endian representation: |
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16. |
Convert the same hex number
(0x000ABC75) to a big-endian representation. |
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17. |
Compute the S/N ratio (in dB)
if signal is 3 watts and noise is 30 milliwatts.
Show your work. |
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18. |
What do the letters FFT
stand for, and what is the purpose of the technique with regard to time or
frequency domain? |
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19. |
What is steganography? |
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20. |
Does the attached article
from the Post describe an instance
of steganography? Why or why not? |